1. Field of the Invention
The present invention relates to an electronic component supplying apparatus for use in an automatic electronic component mounting machine for supplying electronic components one at a time to the electronic component mounting machine which is constructed to automatically mount the electronic components on a printed circuit board.
2. Description of the Prior Art
FIG. 18 of the accompanying drawings shows, in perspective, a continuous electronic-component strip or tape 45 used with an electronic component supplying apparatus of the type concerned. The electronic-component tape 45 includes a series of electronic components 1, such as IC (integrated circuit) chips, held on a carrier tape 4 at equal longitudinal intervals by means of a pressure-sensitive adhesive tape 5 (hereinafter referred to as "adhesive tape") adhering to the individual electronic components 1 through a row of central stamped holes 3 formed in the carrier tape 4 in registry with the respective electronic components 1. Thus, the electronic components 1 of the electronic-component tape 45 has a pitch. The carrier tape has two rows of sprocket holes (feed holes) 2 and 2 formed along its opposite longitudinal edges at equal intervals. The electronic-component tape 45 is wound on a supply reel 6 before it is supplied to a user side at which the tape 45 is unwound from the supply reel 6 for supplying the electronic components 1 one after another to a loading station of an automatic electronic component mounting machine (not shown) for subsequent mounting of the electronic components 1 on a printed circuit board (not shown).
FIG. 13 shows, in front elevation, a conventional electronic component supplying apparatus incorporated in the non-illustrated automatic electronic component mounting machine for supplying the electronic components 1 to a loading station of the automatic electronic component mounting machine where the supplied electronic component is picked up by a vacuum mounting head. In the electronic component supplying apparatus, the carrier tape 4 unwound from the supply reel 6 is guided through first and second guides 7 and 8 onto a feed ratchet 11. In response to rotation of the feed ratchet 11, two rows of pointed feed pins 43 (FIGS. 14-17) successively engage into the corresponding rows of feed holes 2 (FIG. 18), thereby feeding the carrier tape 4 forwardly. During that time, an arcuate tape presser 9 disposed above the feed ratchet 11 guides an upper surface of the carrier tape 4. At the same time, the adhesive tape 5 is pulled downward and subsequently guided in a direction opposite to the direction of movement of the carrier tape 4 by means of a guide 10 disposed below the tape presser 9. Thus, the adhesive tape 5 is separated from the electronic components 1 and the carrier tape 4. The separated adhesive tape 5 is, thereafter, taken up on a take-up reel 37.
When a kicker (not shown) of the electronic component mounting machine moves a pivotable actuating lever 21 in the direction of the arrow A shown in FIG. 13, a lever 18 which is pivoted at its one end by a pin 19 to the actuating lever 21 and, at its opposite end, by a pin 17 to a ratchet arm 16, turns the ratchet arm 16 in the clockwise direction whereupon a feed pawl 15 pivoted by a pin 14 to the ratchet arm 16 slides on teeth on the periphery of the feed ratchet 11 in the clockwise direction (which is opposite to the direction of feed of the carrier tape 4) by an angular distance equal to the pitch of the electronic components 1 of the electronic-component tape 45. A locking pawl 13 pivotable about a pin 12 is provided to prevent the reverse rotation (clockwise rotation) of the feed ratchet 11.
On the other hand, a pusher 22 slidably mounted on a frame 38 via a compression spring 23 is moved downward by an external power source (not shown) to lower one end of a lever 26 pivotally connected to the frame 38 by a pin 24, so that the lever 26 turns about the pin 24 in the counterclockwise direction. In response to the counterclockwise rotation of the lever 26, a connecting rod 28 which is pivoted at its one end by a pin 27 to the opposite end of the lever 26 and, at its opposite end, by a pin 29 to one end of a pivot lever 31, moves leftwards in FIG. 13 to turn the pivot lever 31 about a pin 32 in the clockwise direction. The opposite end of the pivot lever 31 is pivoted by a pin 33 to a feed pawl 34 so that the clockwise movement of the pivot lever 31 causes the feed pawl 34 to slide on teeth on the periphery of the take-up reel 37 by a predetermined angular distance equal to one or several pitches of the electronic components 45 of the electronic-component tape 45.
When the kicker releases the actuating lever 21, the actuating lever 21 returns in the direction of the arrow B in FIG. 13 under the force of a tension spring 25 with the result that the ratchet arm 16 is turned in the counterclockwise direction, thus causing the feed pawl 15 to turn the feed ratchet 11 in the tape feed direction (counterclockwise direction in FIG. 13) by the predetermined distance equal to the pitch of the electronic components 1 of the electronic-component tape 1. Due to this angular movement of the feed ratchet 11, the carrier tape 4 is fed by the feed pins 43 (FIGS. 14-17) of the feed ratchet 11 in the direction of the arrow C by a distance equal to the pitch of the electronic components 1 of the electronic-component tape 45.
On the other hand, the pusher 22 returns to its initial uppermost position. In response to the upward movement of the pusher 22, the feed pawl 34 turns the take-up reel 37 in the counterclockwise direction so that the adhesive tape 5 which has been separated from the electronic components 1 and the carrier tape 4 and guided to the position of the guide 10 is taken up via a guide roller 40 on the take-up reel 37 by a predetermined distance equal to the amount of feed of the carrier tape 4. A tension spring 30 serves to return the pivot lever 31 to its initial position when the pusher 22 moves upwards. A locking pawl 36 pivotable about a pin 35 is provided to prevent reverse rotation (clockwise rotation) of the take-up reel 37.
Operation of the conventional electronic component supply apparatus will be described below in greater detail with reference to FIGS. 14 through 17.
For purposes of illustration, operation of the apparatus begins with parts in the condition shown in FIG. 14 in which a leading electronic component 1a (indicated by hatching for clarity) is held on the carrier tape 4 by a holding power or adhesion of the adhesive tape 5. Then, while the leading electronic component 1a is held under suction by a vacuum mounting head (not shown) of the electronic component mounting machine, the take-up reel 37 is turned counterclockwise to take up the adhesive tape 5 by the predetermined distance. Thus, the adhesive tape 5 is separated from the leading electronic component 1a and the carrier tape 4, as shown in FIG. 15. To this end, the guide 10 is located at such a position that a predetermined length of the adhesive tape 5 is separated from the leading electronic component 1 and the carrier tape 4. Similarly, the guide roller 40 is located at such a position that the adhesive tape 5 is peeled off or separated from the leading electronic component 1a and the carrier tape 4 at an appropriate angle.
Subsequently, the leading electronic component 1a is picked up from the carrier tape 4 by means of the non-illustrated vacuum mounted head, as shown in FIG. 16. Then, the feed pawl 15 (FIG. 13) turns the feed ratchet 11 in the tape feed direction (counterclockwise direction) to advance the carrier tape 4 by a distance equal to the pitch of the electronic components 1 of the electronic-component tape 45. Thus, the next following electronic component 1 is brought into a supply position (loading station of the electronic component mounting machine), as shown in FIG. 17. In this instance, the adhesive tape 5 extends in a slackened condition.
The conventional electronic component supplying apparatus of the foregoing construction is not satisfactory because of drawbacks described below. A rotational force or torque of the take-up reel 37 produced by the action of the tension spring 30 is applied intermittently on the adhesive tape 5. Consequently, when the apparatus is operated at a higher speed to increase the electronic-component supply rate, the adhesive tape 5 is likely to be broken or ruptured due to a tension or pulling force applied abruptly. Thus, a spring force of the tension spring 30 must be determined with due consideration of a shock exerted on the adhesive tape 5 when the adhesive tape 5 is peeled off from the leading electronic component 1a and the carrier tape 4. However, if the adhesive tape 5 has a holding force and a tensile strength that vary irregularly along the length of the adhesive tape 5, it becomes substantially impossible to appropriately set the spring force of the tension spring 30.
In addition, when the adhesive tape 5 has a large holding force, and when the electronic components 1 are small in size, the electronic components 1 tend to be pulled into the corresponding stamped holes 3 when adhesive tape 5 is pulled downwards in response to the intermittent counterclockwise rotation of the take-up reel 37. Furthermore, since the carrier tape 4 while being advanced by the feed pins 43 on the feed ratchet 11 is subjected to a back tension produced mainly by the weight of the supply reel 6, the carrier tape 4 tends to become ruptured from the feed holes 2 when a heavy supply reel 6 is used or when the electronic-component supply rate is increased. Once such rupturing occurs, it is no longer possible to supply the electronic components 1 reliably to the electronic component mounting machine.